The present invention relates to touch panels. More particularly, the present invention relates to force-sensing modules for light sensitive screens.
Touch panels or touch screens capable of providing user interface and user interaction have been widely used in electronic products such as personal computers, cellular phones, personal digital assistants and the like. In operation, it may be necessary for a touch panel to detect a touched position thereon. To detect whether a position is touched, a conventional method called “Carroll method” disclosed in U.S. Pat. No. 4,267,443 to Carroll et al. may be generally employed. In the Carroll method, an optical matrix comprising a plurality of light emitting elements such as LEDs and a matrix of light receiving elements may be arranged on a front surface of a screen. A position at the front surface of the screen where a light beam emitted from a light emitting element may be blocked by the touch of a pen or finger may be detected by the light receiving elements.
Some conventional touch panels or light sensitive screens may detect a change in brightness at a position of the panel due to an approaching or leaving force source and, based on the brightness change, identify whether the position is pressed or touched. For example, an approaching finger or pen may cast a shadow over the position and cause a change in brightness. However, it may be difficult to distinguish a “real” touch that the finger or pen is actually pressed on the position from a “quasi” touch that the approaching finger or pen, though cause a significant brightness change for being very close to the position, does not physically touch or contact the position. A misunderstanding of the touch status may result in malfunction of the panels or undesired operation on the panels.